Sunday, December 26, 2004

There is a fundamental conflict regarding how to determine the effectiveness of cancer screening

Current preventive medicine (apart from immunizations) focuses on cancer screening and coronary artery disease prevention. Cervical cancer screening has moved past the stage of debate. Screening for breast cancer, colon cancer, prostate cancer and lung cancer have not, although different aspects of each are at issue.
In the debate about the value of lung cancer screening a foundational conflict about how decisions are made regarding the effectiveness of screening becomes evident. Specifically, the question becomes which statistical method should be determinative in analyzing the data from randomized population screening trials. Those who believe the final answer lies in disease specific mortality have decided that lung cancer screening is of no value (and this view is the more commonly held one). Dissenters believe that in this type of trial-as opposed to a treatment trial-cure rate or five year survival is the analytic technique that uncovers the truth. A prolific advocate of this dissenting view is Dr. Gary M. Strauss. According to the generally accepted paradigm a reduction in the cause specific mortality in a randomized trial is accepted as the definitive measure of effectiveness. Strauss and others question the assumptions underlying the paradigm.
It gets more complicated. Dr. William C. Black in the Feb. 6, 2002 issue of the Journal of the NCI argues that all cause mortality may be less affected by bias than disease specific mortality. Once the data are collected, and in these screening trials it may take years, the problem remains that there are widely different views as to how to analyze the outcome (i.e what measure of effectiveness do you use) and the method you choose may determine the answer and therefore policy decisions and advice to patients based on the study.
Most of the controversy over lung cancer screening involved trials using chest xrays. As thoracic imaging evolves, similar rhetorical exchanges will likely take place following publications of screening projects with various generations of CT scans.
Does this mean that our ability to use the tools of epistemology lags behind our technological advances?


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